Farshad Moradi1, Richard Buxton1
1Radiology, University of California, San Diego, San Diego, CA, United States
Previous studies found that attention produces robust BOLD modulation with only modest increase in firing activity in primary visual cortex. This could be due to a pure preemptive CBF increase with no relation to local neuronal firing. We tested the presence of such a mechanism using combined CBF/BOLD measurements to estimate relative CMRO2. Results show that attentional enhancement of V1 activity involves an increase of both metabolic activity and blood flow, rather than a preemptive increase in blood flow alone. The ratio of CBF to CMRO2 change appears to be higher when the stimulus is unattended than when attended.